Nanocomposite polymers, fire thermal properties

In general, when compared with the conventional polymer composites, polymer nanocomposites exhibit significant improvements in different properties at relatively much lower concentration of filler. The efficiency of various additives in polymer composites can be increased manyfold when dispersed in the nanoscale. This becomes more noteworthy when the additive is used to address any specific property of the final composite such as mechanical properties, conductivity, fire retardancy, thermal stability, etc. In case of polyolefin/LDH nanocomposites, similar improvements are also observed in many occasions. For example, the thermal properties of PE/LDH showed that even a small amount of LDH improves the thermal stability and onset decomposition temperature in comparison with the unfilled PE [22] its mechanical properties revealed increasing LDH concentration brought about steady increase in modulus and also a sharp decrease in the elongation at break [25]. While in this section, fire-retardant properties and electric properties of polyolefin/LDH nanocomposite were described in detail. 

Fillers are typically used to enhance specific properties of polymers, and the polymer/ nanocomposites based on nanoclays have gained attention because of their ability to improve the mechanical, thermal, barrier, and fire-retardant properties of polymers [3]. Nanosized fillers have been introduced in a wide spectrum of applications ranging from providing photocatalyst activation and conductivity to improve melting... 

The demand for material properties to meet superior and more severe specifications has motivated vigorous research on polymer nanocomposites, that is, polymer matrices incorporated with fillers with at least one dimension in the nanometer range. In a nutshell, these advanced materials exhibit enhanced thermal, mechanical, barrier, and fire retardant properties over virgin polymers [32-37], while their performance depends on the level and the homogeneity of nanofillers dispersion, as well as on the potential for interfacial bonding between the filler and the matrix. 

Composites prepared using different types of nanoparticles can show superior properties compared to pure PU and have a wide range of applications in structural and biomedical fields. The surface morphology of nanocomposites is affected by the nature and amount of the nanoparticles embedded in polymer matrix. Different shapes and sizes of the nanoparticles play a significant role in enhancement of the mechanical, rheological, thermal, and fire retardant properties of the PU nanocomposites. Considerable improvements in antibacterial properties have been reported using nanocomposites compared to pure PU. Incorporation of the different kinds of nanoparticles in PU matrix alters the biocompatible nature of the composites, suggesting that PU composites may have use in biomaterial applications. 

Jash, P. Wilkie, C.A. Effects of surfactants on the thermal and fire properties of poly(methyl methacrylate)/clay nanocomposites. Polym. Degrad. Stab. 2005, 88 (3), 401. 

Overall it is becoming apparent that POSS incorporation into linear polymers or network resins in most cases can lead to nanocomposites with good thermal, mechanical, and fire-retardant properties. As a variety of POSS-containing monomers with functionalized substituents are synthesized, more nanocomposifes will be developed. Furthermore, this technology will be used to modify die matrix resins used for glass or carbon fiber composites. A reduction in the cost of POSS derivatives is key to the further development of apphcations in this area. 

Improvement and new development of methods to prepare new materials, especially new LDHs with a composition and structure compatible with the polyethylene polymer, favouring dispersion of the inorganic nanolayers leading to nanocomposites with improved mechanical and thermal properties and fire resistance. 

PBA-SS nanocomposites were synthesized by a novel, cost-effective, unconventional emulsifier-free emulsion technique. The XRD results showed a disordered layer structure due to intercalation of polymer into the layered silicate. These composites were further characterized by TGA, TEM and their burning rates and exhibited improved properties of thermal stability with good fire retardant properties. It is found that the fire retardant nanocomposites have average biodegradability and have promising future prospects. 

Provided in this chapter is an overview on the fundamentals of polymer nanocomposites, including structure, properties, and surface treatment of the nanoadditives, design of the modifiers, modification of the nanoadditives and structure of modified nanoadditives, synthesis and struc-ture/morphology of the polymer nanocomposites, and the effect of nanoadditives on thermal and fire performance of the matrix polymers and mechanism. Trends for the study of polymer nanocomposites are also provided. This covers all kinds of inorganic nanoadditives, but the primary focus is on clays (particularly on the silicate clays and the layered double hydroxides) and carbon nanotubes. The reader who needs to have more detailed information and/or a better picture about nanoadditives and their influence on the matrix polymers, particularly on the thermal and fire performance, may peruse some key reviews, books, and papers in this area, which are listed at the end of the chapter. 

The impact of the nanocomposite technology on polymers is huge, reflected in enhanced properties of the resulting PNs, such as enhanced mechanical, barrier, solvent-resistant, and ablation properties.12 The effect of nanocomposite technology on the thermal and fire performance of the polymers is primarily observed in two important parameters of the polymers (1) the onset temperature (7( ,nsct) in the thermogravimetric analysis (TGA) curve—representative of the thermal stability of the polymer, and (2) the peak heat release rate (peak HRR) in cone calorimetric analysis (CCA)—a reflection of the combustion behavior (the flammability) of the polymer. The Tonset will be increased and the peak HRR will be reduced for a variety of polymers when nanoscale dispersion of the nanoadditive is achieved in the polymer matrix. 

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